This invention relates to a system for forming a joint, particularly between tubular members of a radiator core and the header having holes through which the tubular members extend to obtain a core unit. The core unit includes a header. Typically, the tubular members are made of solder coated brass and the material of the header is brass. The header has sides which extend above the plane through which the holes are and thus, forms a header pan. The header to be soldered to the tubes is first positioned in a level, horizontal plane. In this first step, the header and tubes to be soldered are fluxed with a zinc chloride flux to clean the mating parts and to remove the outside film from the base metal. The header is then heated normally with a gas torch by a skilled operator and solder wire is fed into the joints around the tubular members which are to be bonded. Typically, a "97 solder" is used which is about 1% tin, 97.2% lead and 1.5% silver and has a melting point of about 588.degree. F. There are various ways of applying this 97 solder. One way is that just described and another way is to dip the tubes extending through the header into a molten bath of "97 solder" and then lift it out and at the same time, blowing air downwardly through the tubular members to remove any molten solder from within those tubular members. The solder rapidly cools and forms an initial seal.
Next it is desired to obtain a second sealing which can be accomplished by the so-called puddling operation in which two torches are used by the operator to melt "40/60 solder" strips which have been placed on the header in the spaces between the tubes which extend up through the header. A composition 40/60 solder is composed of about 40% tin and 60% lead. The header is then heated with a torch by a skilled operator to melt and blow the solder to puddle the entire pan area of the header to a depth of approximately 5/16 inches deep. This operation is most critical in this procedure. Too much heat, too long in one area, will cause the 97 solder to melt and flow out of the joint area. If "30/70 solder" having a melting point of about 491.degree. F. is used in the seams of the tubular members, then it too may melt. When soldering gets too hot, it will run out of the lock and seam joints. This leaves a potential leak problem. Also, during the "97" soldering operation, every tube must have a complete seal and bond around every tube. This insures that no 40/60 will pour through into the fin area. On the other hand, too little heat will cause a pasty condition, resulting in a porous cold solder area, with possible air passages through the puddle layer, resulting in poor strength and leaks with possible entrapment of flux. It should be noted that to obtain maximum strength of the solder involved, the flux must be present and active. The extreme heat of the torches require use of corrosive fluxes, consisting of inorganic gases and salts, which do not char or burn off. These salts remain corrosive after soldering. Complete removal of these salts is necessary to assure that no subsequent corrosion from these salts can take place. The success of this type of solder bonding procedure relys mainly on the ability of the personnel involved.
It is an object of this invention to remove the two main problems in the soldering system just described above. More specifically, an object is to remove the high heat source of the torch which may reach 2000.degree. F. It is a still more specific object of the invention to provide a system which removes or reduces the possible error due to personnel judgment.